Micro-fluidics has been included in various analytical schemes that incorporate the well-known advantages of micro-scale transduction. A basic fluidic operation important in μTAS and Lab-on-a-chip applications is the controlled delivery of minute fluid amounts. The purposes behind hermetic fluid storage and its on-demand delivery, even as a single-use operation, are many fold. For instance, a common micro fluidic application involves the delivery of analytical reagents to a sample to induce transductions that provide information on sample state, like presence or concentration of target chemicals. Intake of samples in portable sensor systems that monitor water bodies is another application that would benefit from automated fluidic delivery. Additionally, automated fluid delivery has been exploited as a way to produce energy “on-demand” by feeding electrolytes into electrochemical cells.
Fluidic delivery mechanisms are known in the art. Pneumatically or inertiallly driven fluidic devices are preferred over electrokinetic mechanisms due to their capacity to provide a wider range of flow rates. CD-styled platforms, based on centrifugal forced actuation, are a classical example of micro fluidic schemes. Volume expanding materials are another alternative that induce pneumatic differentials to obtain micro flow. Applications that involve remote, unattended transducers, for either analytical purposes or power production, have specific requirements that challenge the direct incorporation of some of the available micro fluidic schemes. These include, besides reliability: low-power requirements, and in general, short time constants. A low power device requires that the fluid delivery is done efficiently, thus providing longer operational lives for the power sources and/or more operating device cycles. Fast actuation ensures precise control of the desired transduction. In the case of sensors, reduction of temporal lags guarantees real-time data. An attractive fluidic delivery actuation currently known in the art involves a pressurized liquid reservoir that is contained by a valve, the controllable actuated component, that when opened, delivers a fluid to the desired micro channel. Micro valves, generally activated with low powers, can be utilized for such a scheme.
The design and fabrication of such micro valves is currently known in the art. Polymeric and plastic valves and vents are innovations in micro-valving mechanisms that use non-silicon-based processing. Conventional silicon-MEMS fabrication takes advantages of the technology derived from the integrated circuit industry, such as high yield processing and the capability of wafer level device fabrication, making low-cost production possible.
Accordingly, what is needed in the art is a thermally induced single-use micro valve having low power requirements, short time constants and low-cost production capabilities.